In an electric power steering apparatus the steering assist force is applied to a steering mechanism by driving an electric motor in accordance with steering torque that is applied to a steering wheel by a driver.
Usually, the control of the electric motor is carried out using electronic components. Electronic components can fail abruptly. In this case the steering assist force is no longer present which is uncomfortable for the driver.
The published patent application DE 10 2010 050 818 A1 describes a fail-safe unit which supplies power to the motor even if one of two separate power supply units fails. The power supply units are completely independent from each other. A disadvantage of this solution is that a synchronisation unit is needed, which in the event of failure cannot guarantee power supply to the motor. Further, redundancy means undesired multiple component cost and board area.
Thus a need exists for an improved redundant power supply to an electric motor of an electric power steering apparatus, while keeping the number of components at a minimum to save cost and space.